1. Field of the Invention
The present invention relates to a linear vibrator, and more particularly, to a linear vibrator capable of generating vibrations when mounted in a portable electronic device.
2. Description of the Related Art
Recently, the release of personal portable terminals having large LCD screens provided for user convenience has significantly, increased. Accordingly, a touch screen scheme has been adopted therein, and a vibration motor has been used so as to generate vibrations when a touch is applied to a touch screen.
The vibration motor converts electrical energy into mechanical vibrations using a principle of generating electromagnetic force, and is mounted in the personal portable terminal to be used for silent incoming signal notification.
In a vibration motor according to the related art, a method in which a rotation part of an unbalanced mass is rotated by generating rotational force to thereby obtain mechanical vibrations has been used, and the rotational force is subjected to a rectifying action via a contact point between a brush and a commutator to thereby obtain the mechanical vibrations.
However, a brush-type structure using the commutator may cause mechanical friction and electrical sparks as well as the generation of foreign objects when the brush passes through a clearance between segments of the commutator when the motor is rotated, so that the service life of the motor may be shortened.
In addition, since it takes time to reach an amount of target vibrations due to rotational inertia when voltage is applied to the motor, there may be a problem in which a sufficient amount of vibrations for the touch screen may not be implemented.
A linear vibrator is widely used to implement a vibration function in the touch screen, while overcoming disadvantages in the service life and response properties of the motor.
The linear vibrator does not use a motor rotation principle, but generates resonance by periodically generating, in accordance with resonant frequencies, electromagnetic force obtained through a spring installed inside the linear vibrator and a mass body suspended on the spring, thereby generating vibrations.
In the linear vibrator using the resonance phenomenon, the spring vibrates while being repetitively tensioned and compressed vertically, according to the resonant frequency thereof, under normal conditions, but the spring may vibrate in an undesired direction, rather than providing vertical movement, due to various factors.
This phenomenon may cause undesirable noise as the spring contacts a case to thereby generate noise.
Specifically, even if a desired resonant frequency is added to the linear vibrator, an undesired frequency may also be added to the linear vibrator, and as a result, a undesired mode, i.e., a surging mode in which only the spring vibrates independently of the mass body, may be generated.
When the surging mode occurs, the spring may contact the case, the mass body, or the like, independently of the mass body, and as a result, undesired noise may occur due to the contact.
Accordingly, research into improving the generation of noise by preventing contact between the spring and the case, and the spring and the mass body in the surging mode is urgently required.